This invention relates generally to gas turbine engines and, more particularly, to gas turbine engine blade assemblies.
A gas turbine engine typically includes a plurality of turbine blade assemblies. Each assembly includes a turbine airfoil that extends radially outwardly from a platform, a shank that extends radially inward from the platform, and a dovetail that extends from the shank. The turbine airfoil includes a pressure side and a suction side, which are connected at a turbine airfoil trailing edge. An airfoil root is formed between each turbine airfoil and platform. At least some known turbine blade assemblies include a high-c portion, defined generally as where the airfoil root is tangent to an engine centerline axis. Each turbine blade assembly is circumferentially joined to a rotor disk by the dovetail. Each platform extends circumferentially and axially beyond the airfoil root and defines a leading edge and a trailing edge that are separated by a pressure edge and a suction edge. At least some known platforms have straight pressure and suction edges that extend with a skew angle that is oblique with regard to leading and trailing edges such that an interior angle defined between the leading edge and the suction edge is not equal to 90 degrees. An outer surface of each platform typically defines a radially inner flowpath surface for gas flowing through the turbine blade assembly.
During engine operation, centrifugal forces generated by the rotating airfoils are carried by the airfoils, platforms, shanks and dovetails. The centrifugal forces generate stress in the shanks and dovetails below the platforms. To facilitate reducing stress concentrations, at least some known gas turbines vary, for example, a number of turbine blade assemblies, a platform skew angle, a dovetail skew angle, a dovetail length, a turbine airfoil shape, a dovetail fillet size, a shank transition under the platform, a shank size, a distribution of material in the dovetail, and geometry of seals between turbine blade assemblies. However, increasing the platform skew angle or size of the platform may cause high stresses to be induced in the shank and dovetail under the platform. In addition, because the platform is exposed directly to the flowpath gasses, thermal gradients may also be generated.
In one aspect, a method of fabricating a turbine blade assembly is provided. The turbine blade assembly includes a platform, a turbine airfoil extending radially outward from the platform, a shank extending radially inward from the platform, and a dovetail extending from the shank. The platform includes a leading edge, a trailing edge, a pressure edge, and a suction edge. The method includes forming the platform pressure edge into a plurality of arcs to facilitate reducing stress concentrations and forming the platform suction edge into a plurality of arcs complementary to the pressure edge.
In another aspect, a turbine blade assembly is provided for a gas turbine engine. The turbine blade assembly includes a platform, a turbine airfoil extending radially outward from the platform, a shank extending radially inward from the platform, and a dovetail extending from the shank. The platform includes a leading edge and a trailing edge separated by a pressure edge and an opposite suction edge, the pressure edge includes a plurality of arcs extending between the leading edge and the trailing edge, the suction edge includes a plurality of arcs extending between the leading and trailing edges.
In a further aspect, a gas turbine engine including at least one turbine blade assembly that includes a platform, a turbine airfoil extending radially outward from the platform, a shank extending radially inward from the platform, and a dovetail extending from the shank. The platform includes a leading edge and a trailing edge separated by a pressure edge and an opposite suction edge. The pressure edge includes a plurality of arcs extending between the leading edge and the trailing edge, the suction edge includes a plurality of arcs extending between the leading and trailing edges.